Trace Metals In Seawater: Chelation Capacities, Conditional Stability Constants, And Water Sampler Evaluations (copper, Zinc, Lead)

In this study, the use of anodic stripping voltammetry and copper titrations for the determination of complexation capacity and conditional stability constants for copper-organic complexes in seawater has been evaluated. Pseudopolarogram studies showed that there were two separate polarographic waves corresponding to the reduction of inorganic copper complexes and to the reduction of organic forms of copper. An equation for the calculation of the chelation capacity and the conditional stability constant was derived which takes into account the direct reduction of the copper-organic complexes. When tested with EDTA-seawater solutions, the complexation capacities agreed with the EDTA concentrations to within 10%. The resulting conditional stability constants had a mean of 1.1 x 10(\u278) which agreed well with the value of 1.9 x 10(\u278) calculated from literature stability constant data. The chelation capacity determined using the copper titration/anodic stripping voltammetry technique was also found to agree with that determined using the completely different technique of equilibrium binding gel filtration chromatography.The chelation capacities for Southeastern Florida coastal waters varied from 30 - 195 nmol 1(\u27-1) with a geometric mean of 76 nmol 1(\u27-1). The conditional stability constants for the copper-organic complexes varied from 9.2 x 10(\u277) to 8.3 x 10(\u279) with a geometric mean of 4.2 x 10(\u278). On average, 96% of the copper present in these samples is predicted to be organically complexed.The surface water concentrations of cadmium, copper, lead and zinc were measured at two locations in the western North Atlantic. Samples were collected from the research vessel using a 30 liter Go-flo sampler, and upstream of the ship in 1 liter teflon bottles and in a 30 liter Go-flo sampler. At each station, all of the samples taken with the Go-flo sampler possessed much higher concentrations of zinc (7-10 fold) and lead (2-3 fold) than those collected directly in teflon bottles. No apparent differences were noted for copper or cadmium among the samples collected at each station. The measured values for copper and cadmium in these waters (Southwest Sargasso: Cu 1.8 nmol kg(\u27-1), Cd 0.03 nmol kg(\u27-1); Straits of Florida: Cu 3.0 nmol kg(\u27-1), Cd 0.04 nmol kg(\u27-1)) are in good agreement with recent reports for the western North Atlantic